1. Field of the Invention
The present invention relates to an apparatus and method for manufacturing a steel tube, and more particularly, an apparatus and method for manufacturing a steel tube having an improved surface treatment structure.
2. Background of the Related Art
Generally, methods for manufacturing a steel tube include an injection method and a method of forming a steel plate into a tube shape. Since the injection method is more costly, the method using a steel plate is widely used.
The steel tube manufactured by the steel plate method is referred to as an electric-welded tube, since the steel plate is deformed into a tube shape and its ends are welded together using an electric-resistance welding method.
The method for manufacturing an electric-welded tube is widely employed in most steel tube manufacturing methods, from small to large diameter tubes. A small diameter steel tube manufactured as described above is widely used in a condenser of a cooling apparatus such as a refrigerator, a hydraulic line of a brake system, and other such applications which require high durability and reliability. Therefore, such a small diameter steel tube should be manufactured carefully.
Meanwhile, in order to prevent surface corrosion of a small diameter steel tube, research into more effective surface treatment technology is ongoing.